Simple TCP Echo client.

gistfile1.c

#include <signal.h>
#include <errno.h>
#include <pthread.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#define BUFFER_SIZE 1024

void *client_function(void *ptr);

struct args {
    long id;
    int port;
    char * host;
};

int main(int argc, char *argv[]) {
    pthread_t *threads;
    size_t iret;
    long i;

    signal(SIGPIPE, SIG_IGN);

    if(argc < 4) {
        printf("USAGE: %s NUMCONNECTIONS HOST PORT\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    long num = atoi(argv[1]);

    threads = malloc(num * sizeof(pthread_t));

    for(i = 1; i <= num; ++i) {
        printf("Spawning client %ld.\n", i);

        struct args *a = malloc(sizeof(struct args));

        a->host = argv[2];
        a->port = atoi(argv[3]);
        a->id = i;

        iret = pthread_create(&threads[i], NULL, client_function, (void *) a);
    }

    for(i = 1; i <= num; ++i) {
        pthread_join(threads[i], (void**) &iret);
        printf("Client %ld returned %ld.\n", i, iret);
    }

    free(threads);
    exit(EXIT_SUCCESS);
}

void *client_function(void *ptr) {
    struct args *a = (struct args *) ptr;

    int sockd;
    int count;
    char buffer[BUFFER_SIZE];
    long i = a->id;

    if ((sockd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
        pthread_exit((void *) EXIT_FAILURE);
    }

    struct sockaddr_in serv_name;

    serv_name.sin_family = AF_INET;
    inet_aton(a->host, &serv_name.sin_addr);
    serv_name.sin_port = htons(a->port);

    printf("Trying to connect client %ld...\n", i);
    if (connect(sockd, (struct sockaddr*)&serv_name, sizeof(serv_name)) != 0) {
        pthread_exit((void *) EXIT_FAILURE);
    }

    printf("Client %ld connected!\n", i);
    while (1) {
        if((count = read(sockd, buffer, BUFFER_SIZE)) > 0) {
            buffer[count] = 0;
            printf("Client %ld received: %s\n", i, buffer);
            write(sockd, buffer, count);
        }
    }

    free(ptr);
    close(sockd);
    pthread_exit((void *) EXIT_SUCCESS);
}